I reset a neck on a Gretsch that had a floating bridge,
I rested a straight edge along the fretboard and adjusted the bridge to about an inch in height and when the straight edge matched with neck and bridge that was my angle.
For the speaker I would go for an Eminence 620h, 20 Watts and a hemp cone, best 6" speaker I've heard in a champ.
Get some decent valves/tubes aswell.
Lots of mods you can do to a champ 600ri but those are where I would start.
Give the mojomojo a try
Great pedal, it goes from adding some vintage flavoured hair (Hmmm nice) and goes up to meaty (yummy) overdrive and everything inbetween.
This thing delivers, oh and it's a low cost pedal.